Thanks SpudBlaster I started wtth a long section of pipe and was going to cut to get proper c:b. Is the barrel to long or should it be longer to get proper ratio? Or is the chamber to big? I did hear that I was to pick barrel length and build chamber to match.

[sarcastic] OH! 3 sparks well that make all the difference! for 3 sparks you want a 3.141546467427:1 ratio![sarcastic]

im just kidding. well i didnt run into this problem with my combustion because the pipe was all sch 40 so i just used the od and it was fine because i was comparing apples to apples. if you can give me the id of you SDR pipe i can give yo the volume. generaly for a regulated fuel cannon a .8:1 is good.

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